In reviewing the post I see that there are some good and proven methods about removing the parts
I also see some other issues...
Do you see the slight pitting and 'rust' staining on the rudder
shaft? That is most likely a result of crevice or oxygen corrosion
and I would recommend removing the rudder so the entire
rudder shaft can be examined for pitting. Can be very serious. Pits in stainless steel
can be difficult to inspect and sometimes look like just light pitting and one might think, no big deal. I have inspected thousands of rudder shafts and almost every time I have seen similar pitting, more and deeper pitting is involved. When we cut (cross-section) stainless steel
at the pits we often find that the pits lead to other pitting and holes that best can explained as worm holes the way they take off inside and follow grain structure of the metal.
There also appears to be another problem as well - the blue color you see in the photos is not the 'normal' patina that bronze develops. Normal patina is green. The blue or Turquoise is an indicator of electrical corrosion
of some sort (stray or galvanic). Best to clean the entire fitting and have it inspected for corrosion. It's most likely OK but it warrants a look from a surveyor
or an experienced shipwright or boatyard. An answer of "they all look like that" doesn't cut it. Since the rudder log is bonded, this could be a conduit for electricity or lack of zincs, or...lots of different scenarios so you should at least have the bonding system tested. If you do get the bonding system inspected / tested make sure you get someone that will test to at least the ABYC (American Boat and Yacht Council) standards.
So it looks like there are a few types of corrosion happening here. Post more photos or PM me, happy to help if I can. Good luck to you.